Rab womens nucleus jacket the nucleus hoody is a lightweight two tone fleece in a high stretch double knit fabric for use as a mid layer in cold conditions a comfortable double knit fabric means that the nucleus hoody can be worn as a baselayer in colder winter conditions if the weather is torrid the nucleus will sit comfortably over a baselayer and under a hard shell and will keep the moisture moving through your layers and away from your skin ensuring you stay dry and warm key feature